离散多音调制可见光通信链路的极限速率

Limit Communication Rate of Visible Light Communication Data-link Based on Discrete Multi-tone Modulation

为了从理论上揭示离散多音调制可见光链路极限通信速率与信噪比和误码率水平的关系，分析了发送端／接收端的电光和光电转换关系式及广义可见光通信信道的传递函数．在充分考虑可见光信道时／频域响应的基础上，建立了完备的可见光通信系统数学模型，分析并得到了可见光链路极限通信速率与信噪比和误码率水平的数学关系．分析结果表明，当系统信噪比一定时，极限通信速率与误码率水平呈双e指数增长关系；当系统误码率水平一定时，极限通信速率与信噪比呈波尔兹曼函数关系．在通用的大功率白光发光二极管和PIN探测器参量下，当信噪比为25dB且要求误码率小于10^-3时，系统的极限通信速率为200～228Mbps，该结果与实验报道结果（202～231Mbps）具有较好的一致性．本文给出的理论分析方法和数学模型也可用来估计任意离散多音调制可见光通信系统的极限速率，从而在系统参量优化设计和元器件选型方面具有指导意义．

In order to theoretically reveal the effects of signal-to-noise ratio and the required bit error rate level on limit communication rate of a discrete multi-tone dataqink, in this paper, the electro-optical transfer function of the transmitter, the optical-electro transfer function of the receiver and the total transfer function of generalized visible light communication channel were analyzed. Mathematical modeling of discrete multi-tonevisible light communication system was finally established by sufficiently considering the time and frequency-domain responses of visible light communication channel. Fomulative relations of limit communication rate versus signal-to- noise ratio and bit error rate level were derived. Analytical results show that, under definite signal-to-noise ratio, the limit communication rate reveals double-exponential increasing relation with bit error rate level; under definite bit error rate level, the limit communication rate reveals Boltzmann variation trend versus signal-to-noise ratio. With the universal white light emitting diode and PIN detector, when the signal-to-noise is 25 dB, the limit communication rate is within the range of 2004228 Mbps for requiring a bit error rate of 〈10- 3, which shows good agreement with the reported experimental results （2024231 Mbps）. The novel thereotical analysis methodand mathematical modelling proposed in this paper can also be adopted to evaluate the limit communication rate of any discrete multi-tonevisible light communication system, and therefore they are efficient in system parameter optimization and component selection during the design of such kind of systems.