2005 Fiscal Year Final Research Report Summary
An analysis of propagation characteristics of infrared waves in heavy rain for wireless high speed communications
| Project/Area Number |
16560347
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Communication/Network engineering
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| Research Institution | Toyo University |
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Principal Investigator |
ITO Shigeo Toyo University, Department of Electronics and Communications Engineering, Professor, 工学部, 教授 (30223150)
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| Project Period (FY) |
2004 – 2005
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| Keywords | Transmission Characteristics / Rain / Wireless Communications / Infrared waves |
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| Research Abstract |
Free-space optical communications provide a large capacity at low costs without suffering from any interference between other communication lines. This is also considered to be effective for solving the so-called ‘last mile' problem of optical fiber networks. However, one factor preventing the approval of the free-space optical communication is the degradation of reliability in heavy rain. The research of propagation characteristics during rain was conducted to analyze how the optical wireless communication reliability depends on the rainfall and what causes the bit error rate (BER) in communication link. The observed results for propagation over the 72m and 800m distances show that the sudden drops (dips) in the received optical power cause the BER. The occurrence frequency of the dips for 800m propagation distance is higher than that for 72m even for light rain. The half width of main dips is found to be 0.2-0.3ms and 0.5-0.7ms. However, the profiles with width and depth of dips, appeared in those intervals, are almost independent of the propagation distances. Therefore, although the occurrence frequency for longer distance is higher, the profiles of dips observed at different propagation distances are similar and dips are much more likely to be observed at particular rains. The theoretical approach to the attenuation of optical waves in rain was presented on the basis of the radiative transfer equation with multiple scattering included. The results show that attenuation dependency on the wavelength against rainfall appears and the attenuation is smaller than that usually predicted by the single scattering theory, which are in accordance with the conventional measurements.
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