The Investigation Of Inverse Gaussian Distribution Model For MIMO Wireless Optical Communication

In recent years, due to the high security and low cost, the optical wireless communication (OWC) has received a lot of attention from a large numbers of the researchers, and has become a research hotspot in the field of communication. Because the OWC transmit sound, images and other information by light wave as the carrier directly through the atmosphere, so that the OWC is also often called the free space optical communication. There are many advantages such as wide bandwidth, high security, low cost, high speed on the OWC system, but there are also many defects which limit wide application of the system, such as the stability and reliability of the system in the process of information transmission is very easy to be affected by rain, snow, fog and other bad weather, as well as the atmospheric turbulence in the path of information transmission. Due to the presence of the atmospheric turbulence, there is a series of phenomena which are not conducive to the stability of the OWC system, such as the path attenuation, the beam wander, the beam spread and the pointing error. Therefore, it has important guiding significance and reference value to establish an accurate model that simulate the signal transmission characteristics in the building of an effective, sensitive and low cost OWC system.In this paper, the effect of the atmospheric turbulence on the outage probabilities, error rates and average channel capacities of the OWC system is studied. Finally, the following three achievements are given from the paper:(1) Under the condition that include haze weather, adopt the collimated Gaussian-Schell beam signal source, multi input and multi output (MIMO) transceiver structure and system pointing error (caused by slight jittering of the receiver/transmitter base and minor shaking of the branches in the path of), we adopted the inverse Gaussian distribution model of the signal fluctuation to replace the logarithmic normal distribution model, then established a probability density function model for weak signal fluctuation communication optical path of the received signal.(2) Theoretical model of the average error rates, the outage probabilities and the average channel capacities of MIMO wireless optical communication systems are derived under the equivalent gain combing approximation.(3) The effects of the parameters of transmission distance, light source coherence, receiving/transmitting aperture number and other parameters on the performance of the system are studied, and the conclusions are as follows:The whole wander of the signal beam caused by turbulence is one of the main factors causing the fluctuation of the signal, so that it is also one of the key factors causing increasing of the average bit error rate and outage probabilities and reducing of the average channel capacities.In the process of designing the OWC system, the coherent degree of the light source is also a very important factor, because adopting of spatially partially coherent signal source is one of the effective methods to reduce the system outage probabilities and the bit error rates. But in the MIMO system, too small coherent degree of signal source will result too weak the signal strength at the receivers. When the signal strength is small than the outage threshold of the system, the system will also be broke off, the bit error rates are also increased and the channel capacities are also decreased. The more numbers of the receiving/transmitting apertures, the more the effect of the coherent degree on the system performance. Therefore, in the design of the performance of the system, an optimized spatially partially coherent beam source should be selected to improve the performance of the system according to the structure of the system.Using the equivalent gain combing in the MIMO OWC system, the large beam width is another effective method to improve the performance of the system.In the design of the OWC system, consulting the research results obtained in this paper can effectively improve the design efficiency and system performance.