Research Free Space Optical Communication Diversity Reception Algorithm

With the development of science and technology and economy, people on the performance of the communication network put forward higher and higher requirements. The existing optical fiber communication and microwave communication technology due to high cost, long laying period or carrier bandwidth limitations and other factors, has been difficult to meet network requirements. Free space optical communication (FSO) is a microwave communication technology and optical fiber communication technology combined with the product, at the same time had the high transmission rate of optical fiber communication and microwave communication advantages of flexible access, has become a hot research topic in the field of communications. When the atmospheric channel through the free space optical communication links, atmospheric laser signal transmission will produce a series of effects. In order to restrict atmospheric effects become widely used free space optical communication bottlenecks. Diversity reception of the same information by a plurality of receiving branches, can effectively reduce the influence brought by the atmospheric optical communication system, thereby improving the reception performance of the system.The main work and achievements are as follows:(1) Study the structure of free-space optical communication systems composed of atmospheric transmission system channel modeling, summed up in the turbulence of the four transmission intensity distribution model, Gamma-Gamma distribution, lognormal distribution, negative exponential distribution; spatial diversity reception merge algorithm maximum ratio combining (MRC), equal gain combining (EGC) and selection combining (SC) were studied. (2) Use Meijer-G function, hypergeometric functions or Hermit polynomial to derive accurate or using MRC, bit error rate formula EGC, SC merge algorithm optical communication systems. The results show that the lognormal distribution under the EGC receiver performance slightly inferior to MRC, the worst is SC; collection and three points better than the performance of the algorithm receives no good diversity case.(3) Propose two the improved algorithm of FSO diversity reception selection combining:absolute threshold-generalized selection combining (AT-GSC) and normalized threshold-generalized selection combining (NT-GSC). The results show the reception performance than AT-GSC SC; under certain conditions, the reception performance of NT-GSC is also superior to SC.