Channel Modeling For Terrestrial Free Space Optical Links

PROJECT PROPOSAL Project Title: Channel Modeling for Terrestrial Free-Space Optical Links Group Members: Abdul Basit Ijaz te04 – 0115 Asad-ullah Noor te04 – 0145 Irfan Yaqoob te04 – 0171 Safi Haider te04 – 0113 Faculty Advisor: Dr. S. M. Sajid

A BSTRACT Free-Space Optics (FSO) or Optical Wireless is a line-of-sight technology that refers to the transmission of modulated visible or infrared beams through the air to obtain optical communications. Like optical fiber, Free-Space Optics (FSO) uses lasers to transmit data, but instead of enclosing the data stream in a glass fiber, it is transmitted through the air. The FSO technology has enabled the development of a new category of outdoor wireless products that can transmit voice, data, and video at bandwidths up to 1.25 Gbps. Optical wireless also eliminates the need to buy expensive spectrum for radio frequency solutions. The advantages of free-space optical wireless do not come without some cost. The FSO links must contend with a complex and not always quantifiable subject - the atmosphere. The terrestrial FSO links must deal with the atmosphere just above the surface of the earth, where it has maximum density due to the gravitational force. The terrestrial Free-Space Optical communication channels must be modeled to combat changes in the atmosphere, which can affect FSO system’s performance capacity. The atmospheric attenuators for the terrestrial FSO links are fog, snow, sunlight, rain, absorption, scattering, solar interference and scintillation losses. Some other attenuators include the physical obstructions and the building sway or seismic activity. This project is aiming to provide a simulation for the terrestrial freespace optical channel with precise mathematical models for the most preclusive attenuators. We will able to determine the reliability and the performance of any terrestrial FSO channel for the modeled attenuators through this simulation.

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Given below is a brief over-view of the attenuators which are going to be modeled for the terrestrial FSO channels in this project. i. Fog: Fog is vapor composed of water droplets, can modify light characteristics or completely hinder the passage of light through a combination of absorption, scattering, and reflection. Its attenuation will be modeled. ii. Rain: Rain is also an important attenuator for the optical signals and the specific attenuation for rain has been modeled. iii. Snow: The attenuation due to snow fall will be modeled based on dry or wet snows. iv. Scintillation Losses: Randomly distributed cells are formed under the influence of thermal turbulence inside the propagation medium; the wave fronts vary causing the focusing and defocusing of the beam, called Reflective turbulences. Such fluctuations of the signal are called scintillations. The attenuation caused due to scintillation losses will be modeled.

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