Communication using mid-ultraviolet radiation be tween 200 nm and 280 nm has received renewed attention due to advancements in UV LED emitters and unique propagation characteristics at these wavelengths. Atmospheric gases absorb light at mid-UV so that receivers or sensors operating on the earth's surface receive no interference from solar radiation. This so-called "solar-blind" region of the spectrum allows the use of single-photon detection techniques. Further, UV light is strongly scattered by molecules in the air, enabling non-Iine-of-sight (NLOS) communication. We extend previous work in this area by incorporating angle-dependent Mie scattering into one of the standard propagation models, in an effort to include the effects of aerosols. Experimental results from outdoor measurements using a fog generator are also presented.
In this paper we analyze the performance of random beamforming schemes in a multi-user Gaussian broadcast channel utilizing SINR feedback. For generality, the receivers are allowed to have multiple receive antennas. The first scheme analyzed allows each receiver to feed back the largest SINR it observes for each transmit beam. The distribution function of the maximum SINR is derived and is noted to differ from previous work. In an effort to further reduce feedback, a scheme where each user feeds back the maximum SINR observed over its receive antennas and transmit beams. Using the Fréchet bounds and properties of chi-squared random variables, the throughput of this system is bounded and empirically shown to approach the performance of the previous scheme as the number of users increases.
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