Development Of Link-level Simulation Platform And Research Of Dimming Technology For Visible Light Communication Based On MIMO

Visible light communication (VLC), as an emerging wireless communication technology, can realize the communication function while satisfying the illumination. VLC can take advantage of the huge, no need to be registered and free visible spectrum resources, so as to alleviate the shortage problem of spectrum resources in traditional wireless communication technology. At the same time, VLC uses light emitting diode (LED) as a light source whose energy efficiency is much better than other light sources or RF equipments, thereby it can reduce the environmental pollution problem caused by energy consumption.Therefore, the research of VLC technology is of great significance in the field of wireless communications.The task of this paper is derived from the topic "Visible Light Communication"(No. HIRP020150101) in the Huawei Innovative Research Project (HIRP). As the frequency response bandwidth of LED is limited, the communication rate of a single LED is relatively low;moreover, due to the luminous intensity of a single LED is limited, its qualities of lighting and communication are poor. Therefore, it is necessary to utilize multiple LEDs simultaneously to improve the communication rate and increase the optical power, so as to meet the requirements of lighting and communication, which makes VLC naturally have the characteristics of multiple-input multiple-output (MIMO). In this paper, the visible light communication system based on MIMO(MIMO-VLC for short) is researched, and the main research contents are as follows:Firstly, in this paper, the hardware and software simulation platform system of the visible light communication (VLC) system is researched,and the development of MIMO-VLC link-level simulation platform based on the VLC protocol (IEEE 802.15.7) is realized. The platform is based on the specifications of PHY ? (corresponding to outdoor) and PHY ?(corresponding to indoor) in the IEEE 802.15.7 protocol, and can implement all the operating modes (PHY ?.a ? i and PHY ?.a ? n)contained in the protocol, so as to provide a foundation platform of link-level communications corresponding to the operating modes for various outdoor applications (intelligent transportation, etc.) and indoor applications (indoor positioning, dimming, etc.).Secondly, for the indoor illuminating system, VLC needs to realize dimming function, but the dimming schemes proposed by the current research of dimming technology have not fully utilized some of the characteristics of MIMO to improve communication performance.Aiming at this problem, a dimming scheme based on antenna selection for MIMO-VLC in a single-lamp scenario is proposed. This scheme selects the antennas with smaller optical power attenuations to be active according to the channel state information by incremental and decremental algorithms, and the total number of active antennas is proportional to the dimming proportion, so as to optimize the communication performance and improve the quality of communication while realizing the dimming function. With arbitrary receiving position and dimming proportion, the communication performance of the proposed dimming scheme in this paper is superior to that of the traditional dimming scheme based on amplitude adjustment.Thirdly, in the aspect of the illuminating function, VLC sometimes needs to consider the requirments of the illuminance range and the uniformity illuminance ratio, but the current dimming schemes and the proposed dimming scheme in a single-lamp scenario have not consider the requirment of the illuminance range, and the latter can not meet the requirment of the uniformity illuminance ratio. Aiming at this problem, a dimming scheme based on antenna selection for MIMO-VLC in a multi-lamp scenario is proposed. This scheme satisfies the requirement of the uniformity illuminance ratio by properly allocating the number of active LEDs in each lamp and satisfies the requirement of the illuminance range by limiting the minimum value of the dimming proportion; and then, the optimum combination is selected from all the LED's number combinations satisfying the above two requirements. With arbitrary receiving position and dimming proportion, the proposed dimming scheme in this paper can meet the above two requirements and its communication performance still outperforms that of the traditional dimming scheme based on amplitude adjustment.